Nowadays developments in electronic industries are tending towards making things lighter, thinner, more compact and rapid. Among the development trends, organic material plays an important role due to its potentials to make lighter, thinner and smaller products. Seeing this, it is apparently important for the electronic industries to develop highly functional and thermosetting organic material.
Polyethersulfone, with the properties of nice heat- and impact-resistance, can be applied in shoot-and-add processes and used as recovery material. However, just because its good heat-resistance, polyethersulfone can resolve in solvents of a high boiling point only, such as N-methylpyrrolidone, N, N-dimethylformamide etc., and cannot be processed and produced below 150xc2x0 C. Furthermore, as a product of thermally moldable plastics with lower glass transition temperature (Tg) and melting point, it cannot be used, either, as adhesives for electronic industries, for instance, adhesives for Lead On Carrier (LOC), 3-layer and Double-side FPCs, and CSP motherboards. Therefore, it has become an important issue in development and research of new polyethersulfone how to improve its properties and enable it to be dissolved in solvents of low boiling point ( less than 150xc2x0 C.) and hot pressed below 200xc2x0 C. without losing its high heat-resistance characteristics. As a result, the invention said hereof successfully develops a brandnew polyethersulfone that can be dissolved in such ether solvents as THF,1,4-Dioxane, etc.
With the glass transition temperature (Tg) lower than 130xc2x0 C., the polyethersulfone resin developed by the invention can be hot pressed at a temperature ranged from 180xc2x0 C. to 220xc2x0 C. Besides, the newly developed polyethersulfone resin has unsaturated double bonds that enhance its heat-resistance ability after thermally hardened. Generally speaking, it is not suitable for thermally hardened resins to be baked at a high temperature lest that it will lose the properties gained from hot pressing. Fortunately, the invention has successfully developed a soluble thermosetting polyethersulfone resin to overcome the above-said chemical disadvantages and, at the same time, effectively improve the thermosetting ability of substances composed by polyethersulfone resin. As you can see, the invention""s greatest achievement is to meet all the characteristics listed below:
(1) With polyethersulfone contain the unsaturated double bonds that raise the Tg of thermosetting polyethersulfone over than 170xc2x0 C.,
(2) with the Tg less than 130xc2x0 C. before hardened so that the polyethersulfone developed by the invention can be have the hot pressed character.
(3) making polyethersulfone resin soluble in ether solvents like THF,1,4-Dioxane so that it can be keeps its hot pressing properties even through brushed on polyethersulfone resin then heating at a lower temperature of 150xc2x0 C.
(4) increasing elongation of polyethersulfone resin more than 3% after hardened at 200xc2x0 C., and thus give polyethersulfone resin have certain mechanical strength. The characteristics of production that bring about the useful of adhesives for Lead On Carrier (LOC), 3-layer and Double-side FPCs, and CSP motherboards.
As a known engineering plastics, polyethersulfone resin has a better thermosetting ability than substances of the same structure such as polyethersulfone resin and polythiolether resins. However, just its outstanding thermosetting considerably limits its applications in processing to an extent that it is not so often used as polybenzeylether and polythiolether resins. That""s why there are rare factories that would like to produce polyethersulfone resin.
Two ways in which polyethersulfone resin is synchronized and applied are adopted at present: one is used as engineering plastics, plastic grinds and separate membrane produced via shoot-and-add processing for wear-proof, impact- and thermosetting components; the other is used in composition of recovery material to improve the impact-, heat- and moisture-resistance properties of the said recovery material for sports devices and aviation material.
As to previous know-how of polyethersulfone concerned, most of its researches are focused on synthesize of plastics of high molecular weights and different structures, and only a few on amine terminated polyethersulfone oligomer, as stated in U.S. Pat. No. 5,071,941, U.S. Pat. No. 5,917,137, U.S. Pat. No. 3,824,293, U.S. Pat. No. 5,089,560, WO Patent No.96/117,006, and EP Patent No.193,082. The above mentioned patents are all concerned about synthesize and application of polyethersulfone, but differ completely from the technology of the invention.
The subject of U.S. Pat. No. 5,071,941 is terminated cyclical-structured, unsaturated double-bond polyethersulfone oligomer. The polyethersulfone oligomer comes from hydroxyacrylamine compound formed by hydroxyldiamine compound and cyclical-structured, unsaturated double-bond acid anhydrides. However, the hardening process of such structure really takes time and, even more, this kind of production process cannot be applied to acrylic production structures.
U.S. Pat. No. 5,917,137 is applied in producing gas phase separate membrane form by polyethersulfone resin and polyimide resin. Since the polyethersulfone used in U.S. Pat. No. 5,917,137 is common marketed engineering plastics and is only one component of their subject, it is entirely different from the invention in its structure, chemical characteristics and application property.
WO Patent No.96/17,006 is focused on formation of compound material, like reinforced fiber and strong fiber, composed of thermosetting thermoplastic resin, Melamine-formaldehyde, hardener and glass fiber, with improved impact-, moisture- and thermosetting. A detailed analysis of the contents of WO Patent No.96/17,006, it can be found that polyethersulfone, polyesteramide, and polyethersulfone resin are used as thermosetting thermoplastic resin, and the three of which are all commercialized products. In WO Patent No.96/17,006, thermosetting thermoplastic resin is adopted to synchronize reinforced and strong fiber compound material, both used as the compound material for sports devices. The main difference from the invention is that the thermoplastic resin used in WO Patent No.96/17,006 does not cross-link with Melamine-formaldehyde and even no self cross-linkage occurs, but the thermoplastic resin used in the invention will cross-link with each other. Seeing this, it is apparent that the polyethersulfone of the invention already has completely different chemical characteristics. In EP Patent No. 0,193,082, amine terminated polyethersulfone oligomer, hardener, Melamine-formaldehyde and fiber cloth are used as main material to produce matrix resins for aviation compound material. The polyethersulfone oligmer used in EP Patent No.0,193,082 has a molecular weight less than 10,000 and the number of amine group in a single molecule unit less smaller than 1.4, and does not work well in cross-linkage with Melamine-formaldyhide. Even worse, this kind of amine terminated polyethersulfone oligmer cannot form a cross-linkage structure in itself. Such a cross-linkage structure may occur only in reaction with some other kinds of resins like Melamine-formaldehyde.
In U.S. Pat. No. 3,824,293, hydroxyl or thiol metallic salt, acted with reactive haloaromatic compound, is used to form thermosetting thermoplastic resins or oligmers such as polyethersulfone thioether resin, polythioethersulfone resin, and polythioethersulfone ester resin. The molecular weight of the oligmers produced in this Patent is less than 10,000, and each molecule has only two hydroxyl groups (acted with Melamine-formaldyhide). Thus, no cross-linkage is formed.
In U.S. Pat. No. 5,089,560, compound material with phase-separated and multi-phase morphology structures is produced with amine terminated polyethersulfone oligmer, acrylonitril butadiene rubber particles, Melamine-formaldehyde, hardener and fiber, etc. Because of the acrylonitrile butadiene rubber particles included, there is phase-separated phenomenon occurs and the glass transition temperature (Tg) is reduced.
From the above know-how comparison, it is remarkable that the polyethersulfone of the invention has a completely renewed structure by introducing in a brandnew way the above-said unsaturated double bonds into the typical polyethersulfone resin structure, making it totally different from thermoplastic resins and the organic functioned polyethersulfone resin. As you can see, the features of the invention are: soluble in solvents of low boiling points, Tg less than 130xc2x0 C. before hardened, and Tg greater than 170xc2x0 C. after hardened.
The purpose of the invention is to find out a soluble thermosetting polyethersulfone resin by using a new structural design, with its heat-resistance and shoot-and-add processing greatly improved. To obtain heat-resistance up to a certain extent, polyethersulfone resin of aromatic structure is used as the main component of the chain structure in the invention. Then, a side-chain structure-the aliphatic unsaturated double bonds, is introduced into the structure of polyethersulfone resin. By this way, the thermally hardening polyethersulfone resin can be acquired, which is soluble in ethyl ether solvents, thermosetting and able to be hot pressed.
The polyethersulfone resin of the invention is made via a delicately designed producing process by using commercialized chemicals as its material. In the invention, we employ dihalodiphenylsulfone reacted with aromatic dihydroxyphenyl compounds to form a special kind of polyethersulfone resin that has hydroxycarboxy groups at its primary chain structure; and then, taking use of the special acting properties of the hydroxycarboxyl, epoxy and hydroxy groups, to form unsaturated double bonds at the molecular side chains.
Any one who is familiar with the above-said knowhow will get a clear image of the strong and weak points of the invention disclosed hereof after reading the detailed illustrations of the preferred demonstration diagrams below.